Identification of ribosomal proteins S2 and L10a as tumor antigens recognized by HLA-A26-restricted CTL

c-Myc targeted regulators of cell metabolism in a transgenic mouse model of papillary lung adenocarcinoma

c-Myc's role in pulmonary cancer metabolism is uncertain. We therefore investigated c-Myc activity in papillary lung adenocarcinomas (PLAC). Genomics revealed 90 significantly regulated genes (> 3-fold) coding for cell growth, DNA metabolism, RNA processing and ribosomal biogenesis and bioinformatics defined c-Myc binding sites (TFBS) at > 95% of up-regulated genes. EMSA assays at 33 novel TFBS evidenced DNA binding activity and ChIP-seq data retrieved from public repositories confirmed these to be c-Myc bound. Dual-luciferase gene reporter assays developed for RNA-Terminal-Phosphate-Cyclase-Like-1(RCL1), Ribosomal-Protein-SA(RPSA), Nucleophosmin/Nucleoplasmin-3(NPM3) and Hexokinase-1(HK1) confirmed c-Myc functional relevance and ChIP assays with HEK293T cells over-expressing ectopic c-Myc demonstrated enriched c-Myc occupancy at predicted TFBS for RCL1, NPM3, HK1 and RPSA. Note, c-Myc recruitment on chromatin was comparable to the positive controls CCND2 and CDK4. Computational analyses defined master regulators (MR), i.e. heterogeneous nuclear ribonucleoprotein A1, nucleolin, the apurinic/apyrimidinic endonuclease 1, triosephosphate-isomerase 1, folate transporter (SLC19A1) and nucleophosmin to influence activity of up to 90% of PLAC-regulated genes. Their expression was induced by 3-, 3-, 6-, 3-, 11- and 7-fold, respectively. STRING analysis confirmed protein-protein-interactions of regulated genes and Western immunoblotting of fatty acid synthase, serine hydroxyl-methyltransferase 1, arginine 1 and hexokinase 2 showed tumor specific induction. Published knock down studies confirmed these proteins to induce apoptosis by disrupting neoplastic lipogenesis, by endorsing uracil accumulation and by suppressing arginine metabolism and glucose-derived ribonucleotide biosynthesis. Finally, translational research demonstrated high expression of MR and of 47 PLAC up-regulated genes to be associated with poor survival in lung adenocarcinoma patients (HR 3.2 p < 0.001) thus, providing a rationale for molecular targeted therapies in PLACs.

Mitochondrial DNA plasticity is an essential inducer of tumorigenesis

Although mitochondrial DNA has been implicated in diseases such as cancer, its role remains to be defined. Using three models of tumorigenesis, namely glioblastoma multiforme, multiple myeloma and osteosarcoma, we show that mitochondrial DNA plays defining roles at early and late tumour progression. Specifically, tumour cells partially or completely depleted of mitochondrial DNA either restored their mitochondrial DNA content or actively recruited mitochondrial DNA, which affected the rate of tumorigenesis. Nevertheless, non-depleted tumour cells modulated mitochondrial DNA copy number at early and late progression in a mitochondrial DNA genotype-specific manner. In glioblastoma multiforme and osteosarcoma, this was coupled with loss and gain of mitochondrial DNA variants. Changes in mitochondrial DNA genotype affected tumour morphology and gene expression patterns at early and late progression. Importantly, this identified a subset of genes that are essential to early progression. Consequently, mitochondrial DNA and commonly expressed early tumour-specific genes provide novel targets against tumorigenesis.

Expression profile of ribosomal protein L10a throughout gonadal development in rainbow trout (Oncorhynchus mykiss)

Ribosomal protein L10a (RpL10A) has been previously established as a stimulator during the early stages of ovarian development in both the banana prawn and the fruit fly. In order to develop a greater understanding of the role of this protein in vertebrates, the present study aimed to characterize the expression profile of rpl10a during gonadal development in fish. It was determined that the expression of rpl10a within genital ridges increased during embryonic development. Although rpl10a expression was observed in both gonadal somatic cells and primordial germ cells, higher levels of both transcript and protein expression were detected in somatic cells. rpl10a transcripts were observed in all of the adult tissues examined. Cellular level expression of rpl10a was subsequently characterized across various maturational stages using in situ hybridization and immunohistochemistry of both testes and ovaries. Analysis of tissue derived from the testis showed high levels of rpl10a expression within spermatogonia and the Sertoli cells attached to them. In ovarian tissue, rpl10a was strongly expressed in chromatin-nucleolus-stage and peri-nucleolus-stage oocytes. The relationship between rpl10a expression and regulation of gonadal development was confirmed using real-time PCR, which was performed in order to analyze rpl10a expression in testicular and ovarian tissues subsequent to incubation with salmon pituitary extract and various sex steroids for 24 h. Among them, 11-ketotestosterone at 100 ng/mL effectively up-regulated expression of rpl10a in testicular tissues, while 17β-estradiol down-regulated rpl10a expression in ovarian tissues. These results suggested that rpl10a played a role in the regulation of gonadal development in fish.

A novel approach to biomarker discovery in head and neck cancer using an autoantibody signature

Despite the dismal prognosis for patients with squamous cell carcinoma of the head and neck (SCCHN), there have been no novel treatments in over 40 years. Identification of novel tumor antigens in SCCHN will facilitate the identification of potential novel treatment targets. Tumor antigens are proteins selectively expressed by tumor cells and recognized by the host immune system. Phage-displayed tumor antigens were enriched by biopanning with normal and then SCCHN-specific serum. Ninety-six phage clones were sequenced for identification, and 21 clones were validated using Luminex. One of these proteins, L23, a novel tumor antigen in SCCHN, was validated as an oncogene. L23 is upregulated in SCCHN compared with normal keratinocytes. Knockdown of L23 inhibited proliferation, invasion and cell survival. Overexpression of L23 had the reverse effect. Overexpression of L23 in non malignant cells led to transformation. Injection of SCCHN cells with knockdown of L23 in mice, induced tumors that were significantly smaller than control tumors. In conclusion, the immunomic screen yielded a panel of antigens specific to SCCHN; one of these proteins, L23, is a novel oncogene in SCCHN.

RpL10A regulates oogenesis progression in the banana prawn Fenneropenaeus merguiensis and Drosophila melanogaster

To develop banana prawn (Fenneropenaeus merguiensis) aquaculture, the mechanism of ovarian maturation is under investigation. In a previous study, we reported the RpL10A protein as an ovarian maturation stimulator. To further investigate the function of RpL10A, we turned to the fruit fly (Drosophila melanogaster) to take advantage of the genetic tools available. Here, we elucidate the expression and function of RpL10A in the D. melanogaster ovary. RpL10A is expressed in the cytoplasm of both nurse and follicle cells throughout oogenesis. While shrimp have one RpL10A gene, D. melanogaster has two genes, RpL10Aa and RpL10Ab. RpL10Ab displays more similarity with shrimp RpL10A and was further investigated. RpL10Ab homozygous mutants are lethal and germline clone analysis showed that RpL10Ab is an essential gene in oogenesis. Moreover, RpL10Ab(-) germline clones resulted in premature death of the follicle cells. This phenotype is reminiscent of some insulin pathway mutants, suggesting that RpL10Ab may be involved in the insulin signaling pathway. In addition, RpL10Ab(-) follicle cells showed abnormal nuclei and membranes. Shrimp RpL10A rescued RpL10Ab homozygous mutants, revealing their functional conservation. Surprisingly, we found cell death in multiple tissues when RpL10A was over-expressed, suggesting that proper RpL10A levels are important. This research reveals novel findings about the role of RpL10A during oogenesis and may, in the future, lead to new approaches to stimulate ovarian development in shrimp.

Characterization and biological activity of the ribosomal protein L10a of the white shrimp: Fenneropenaeus merguiensis De Man during vitellogenesis

The molecular events in the ovaries of Fenneropenaeus merguiensis De Man during vitellogenesis were investigated. The ribosomal protein L10a (RPL10a) was characterized and cloned. It consisted of 669 bp and the deduced polypeptide had 217 amino acids (GeneBank/EBI accession number FJ623402). The calculated molecular mass and pI were 25.7 kDa and 10.06, respectively. An immunohistochemical technique showed that RPL10a was located in the cytoplasm and nucleus of developing oocytes and follicle cells. Treatment of undeveloped ovarian explant cultures with recombinant histidine (His)-RPL10a stimulated the expression of translationally controlled tumor protein (TCTP), heat shock protein 70 (HSP70), and shrimp ovarian peritrophin (SOP) genes, previously shown to be involved in ovarian maturation. The transcripts of all three genes in the ovarian explants showed their highest expression after 4 h incubation with the His-RPL10a at 37 degrees C. The TCTP and HSP70 transcripts declined after 12 h, while the transcript of SOP remained high until 24 h. The His-RPL10a did not stimulate the expression of the TCTP, SOP, and HSP70 genes in shrimp muscle tissue. The information on the molecular behavior of the RPL10a in this study may, in the future, lead to new methods to stimulate ovarian development in shrimp.

Ribosomal versus non-ribosomal cellular antigens: factors determining efficiency of indirect presentation to CD4+ T cells

Proteins released from dying cells can be taken up and presented by antigen-presenting cells (APC) to T cells. While the presentation of such self antigens may lead to beneficial anti-tumour responses, in autoimmune disease it leads to pathological immune responses. The sub-set of self proteins targeted in autoimmune disease is circumscribed, and certain cellular components such as ribonucleoprotein (RNP) complexes are often targeted. Although explanations for this antigen selectivity have been proposed, there has been little direct testing of these hypotheses. We and others previously showed that ribosomal proteins, targeted in autoimmune disease, are also targets of anti-tumour T-cell responses. We asked whether particular properties of ribosomal proteins such as incorporation into RNP complexes or sub-cellular localization enhance ribosomal protein presentation by APC to CD4(+) T cells. Ribosomal protein antigens within purified intact ribosomes or free of the ribosomes were equally well taken up and presented by APC, demonstrating that inclusion of ribosomal proteins into an RNP complex does not confer an advantage. However, antigens localized to ribosomes within apoptotic cells were less efficiently taken up and presented by APC than the same antigens localized diffusely throughout the cell. This suggests that presentation of ribosomal proteins is somehow down-regulated, possibly to facilitate presentation of other less-abundant intracellular proteins. Consequently, the explanation for the frequent targeting of ribosomal proteins by both autoimmune and anti-tumour T-cell responses is not at the level of uptake from apoptotic cells and must be sought elsewhere.

Expression and functional study of ribosomal protein L5 in gastric cancer

AIM: To investigate the expression of ribosomal protein L15 (RPL5) in gastric cancer as well as its effect on the proliferation of gastric cancer cells.

METHODS: The expression of RPL5 was detected in gastric cancer cell lines AGS, MKN45, SGC7901 and MGC803 by Western blot. The specific siRNA vector of RPL5 was constructed and then transfected into AGS cells. The expression of RPL5 in the transfectants was examined by Western blot. The growth of transfected cells was evaluated by MTT assay and flow cytometry.

RESULTS: The expression of RPL5 in gastric cancer cell lines AGS, MKN45, SGC7901 and MGC803 were all significantly higher than that in GES-1 and normal epithelial cells of gastric mucosa. The specific siRNA vectors of RPL5, named U6-RPL5A and U6-RPL5B, were successfully constructed and transfected into AGS cells. U6-RPL5A could inhibit the expression of RPL5 significantly. The growth rate of U6-RPL5A transfected cells, named AGS-U6-RPL5A, was lower than the control cells, and the percentage of the cells that was in proliferation phase was decreased by about 5%.

CONCLUSION: RPL5 can inhibit the proliferation of gastric cancer cells, and further investigation of RPL5 function will be helpful in the diagnosis and treatment of gastric cancer.